Did leftists distance themselves from the shooter of Scalise and others two months ago? That was a literal targeted assassination attempt of a USG official.
There is a massive difference between mowing down innocent people and assassinations on politicians. The latter have bodyguards for exactly that reason, and that's why assassinating a politician is, well, an assassination, and what that 20-year-old Nazi did yesterday is an act of domestic, right-wing terrorism.
(for the record, I personally do not like assassinations)